Jean Prestet (1648–1691) was a French Oratorian priest and mathematician who contributed to the fields of combinatorics and number theory. Prestet grew up poor. As a teenager, he worked as a servant of the Oratory of Jesus in Paris. He was promoted to scribe for Nicolas Malebranche, who taught him mathematics. The book contained a proof of Descartes' rule of signs that Prestet later acknowledged to be incomplete. It also included a generalization of Euclid's lemma to non-prime divisors.